The present invention relates to an absorbent composition particularly useful as an animal or pet litter and a process for making the improved absorbent composition.
It is the habit of house-broken animals, such as cats, to deposit their waste material in a specially-provided litter box. Similarly, untrained and caged animals urinate and defecate on the floor of their cage, often in approximately the same floor area of the cage. Litter material useful for collecting the urine and feces of small animals is made of various absorbent compositions and generally contains a large amount of clay and/or cellulosic materials. After a relatively short period of time, the dross-soiled absorbent material emits objectionable odors because of the presence of the urine and fecal matter.
In order to reduce the odors, it is common practice to periodically physically remove the feces from the litter. This results in some reduction in the odors due to the feces, but has no effect on the odors caused by the urine. When the odors from the urine become intolerable, it is a common practice for the homeowner to discard the litter entirely. The homeowner then washes the litter box and refills it with fresh litter.
The most commonly used litter box absorbent materials are clays. Swelling clays are one means for facilitating separation and removal of urine-soaked clay particles from an otherwise fresh bed of animal litter. Such clays expand in volume and become tacky when wetted, forming clumps or agglomerates of spent clay which can be individually removed from the bed. U.S. Pat. No. 5,000,115 describes a method and a composition of absorbing animal dross using a water-swellable bentonite clay. The absorbing composition disclosed in the U.S. Pat. No. 5,000,115 patent requires a sufficient amount of fines for the litter material to clump when wet.
Animal litters which form gelled agglomerates when in contact with excreted animal body fluids are described in U.S. Pat. Nos. 4,685,420 and 5,014,650. U.S. Pat. No. 4,685,420 discloses an animal litter that contains a dry blend of a porous, inert solid substrate, such as particulate clay, and a particulate water-absorbent polymer. The animal litter disclosed in U.S. Pat. No. 5,014,650 is a dry blend of a porous, inert solid substrate, and a dry particulate cellulosic ether as a water-absorbent polymer.
The clumping animal litter facilitates the removal of urine-soaked particles, but the animal litter remains dusty during manufacture as well as when dispensing, particularly when the bulk of the litter is clay. In addition, in animal litters containing a cellulosic ether or water-absorbent polymer, there is the possibility that the cellulosic ether or water-absorbent polymer will segregate from the particulate inert solid substrate during handling and shipping.
To reduce the dust associated with clay containing animal litters, U.S. Pat. No. 5,101,771 discloses an animal litter containing discrete, free-flowing and non-swelling clay particles and a water-soluble organic resin clumping agent in an oleaginous vehicle, such as mineral oil, distributed on the surface of the free-flowing clay particles.
Animal litter has also been produced by mixing clay fines with an adhesive-type binder, such as a water-soluble lignin, and the clay-binder mixture then converted into pellets through the action of a pin-type solids processor as disclosed in U.S. Patent 4,704,989. Fines were defined as a range of particles less than about 40-200 mesh in size. Pellets formed in this manner were reported to have a total surface absorption and total absorption capacity in the open pore spaces approaching the capacity of clay fines. A process for producing animal litter from fines which pass a 30-50 mesh is disclosed is U.S. Pat. No. 4,686,937. The process includes mixing an aqueous solution of lignin with clay fines, transferring the clay-lignin particles to a disc pelletizer having a screw conveyor to feed the particles through a die and then forcing the clay-lignin particles through the die and cutting the coherent mass obtained from the die to form the material into pellets.
U.S. Pat. No. 4,409,925 discloses a method for producing a granular light-weight absorbent material by mixing ground paper, Plaster of Paris and at least one additional component to form a homogeneous mixture, spray applying water droplets to the homogeneous mixture and then mixing the water and mixture to form discrete particles.
Other patents generally dealing with animal litter or absorbent materials include, for example, U.S. Pat. Nos. 4,881,409; 4,591,581; 4,638,763; 4,844,010; 4,021,011; 4,622,920; 4,657,881; 5,152,250; 5,147,877; 4,409,925 and 4,883,021.
Despite the improvements in producing a consumer acceptable animal litter, a need still exists for a litter box absorbent material that effectively collects the urine or other dross material and that agglomerates when wetted to allow physical removal of the wetted litter box absorbent material from the unwetted litter box absorbent material. In addition, the need exits for an effective process for producing a relatively dust-free clumping animal litter that uniformly distributes additives throughout the litter mixture.